Hello again, NAM.

Okay so here's what I got: '11 MCS. Just hit 56k miles. Manic stage 1 and a few other bolt-ons listed in my sig.

Recently I put the hammer down straight out of the dirveway (fool's move, I know) I had a big misfire and the car ran rough at idle afterwards. Checked the spark plugs and the #4 (driver side) plug was busted. The ceramic sleeve around the very tip was movable. I suspect a detonation actually. No big deal, I think. I order some NGK plugs online and to hold me over I bought an Autolite plug from Autozone to hold me over.

First problem is here. The autolite plug wouldn't torque to the advised 14 lbs/ft. It would actually pop out of the threads before getting there. And when I tried to get it as tight as I could and started up it blew out of the motor and popped the coil pack out.

Thankfully I got the old busted NGK plug back in, torqued it appropriately. I hobble my car over to a local shop in limp mode now and get some better fitting Denso plugs. Gapped them properly. Everything is good, or so I thought.

New plugs made the CEL and limp mode go away. The idle smoothed out, but now under hard acceleration, more so on the tune than stock ECU map, the engine stutters and misfires with no CEL so far. I had a similar issue when I first got the Manic tune and it was a faulty coil pack, but I've tested all my coils and swapped them around numerous times (I have a collection of 7 good ones now) to no avail. No difference.

What's going on? I see a possibility of a HPFP. But also I suspect something else broken inside my cylinder 4 like an injector or valve considering I broke a spark plug (pics of that below).

https://i.imgur.com/vRWUgIQ.jpg
https://i.imgur.com/4DXoBUC.jpg

I've already been to my mechanic who specializes in BMW/VAG twice int he last month with a broken brake caliper bolt and a dead key fob. My wallet would rather I not go back there any time soon.

 

I recently read somewhere on NAM that our coils are designed for Iridium plugs, and substituting other materials is a bad idea. Are you sure your temporary plugs are Iridium?

 

They are iridium but I've read that people have had trouble with Denso plugs in general for some reason.

 

Grab some new NGK 1422 (I think) and gap to .25
Cannot understand the plug popping out issue; are the thread damaged and if so why don't the NGK's pop out?
My r56 JCW with Manic 3+ has real issue with plugs w a stock gap.

 

Your guess is as good as mine on the Autolite but they're getting an earful from me when I return it tomorrow. I think the thread is just plain too small.

I ordered NGKs through amazon and I'll have them soon. I'm going to have to ride out the Densos until then but they don't give me too much trouble on the stock map.

I had no trouble with NGKs on the factory set gap before just that one freak thing that blew up my plug. Should've just gone with that from the start.

 

I'm in a similar boat. Mine started with a huge fire ball from the tail pipe at 6k wot. I discovered my down pipe was extremely loose at the turbo and was probably giving wacky AFR's. Tightened everything up and all was well for a couple weeks. Temps dropped into low 40's and it started with rough idle at startup, then the occasional fire ball at the top end, then it drove like it was firing only two cylinders at 5psi until fully warm, then the two cylinder symptom with any throttle input and limp mode. All that within ten days. Then it started to get better on its own within ten miles, now i'm almost trouble free.

Played musical plugs and coils, and think I've isolated it to cyl #3 by disconnecting coils one at a time while it was running extremely bad and #3 made no change when disconnected. Swapped coils, then plugs and symptom seems to stay with 3, but the car hasn't run bad enough to get a discernible result. This leads me to think the injector could be funked up. Right now the only problem I have is a rough idle and the half yellow engine light on cold starts for a minute or so. I'm honestly thinking I pumped 8 gallons of regular gas.

87k on the car.
27k on the NGK 1422 plugs and Manic 2 tune
10k on the fuel filter.

 

Well something caused that one plug gap to close up completely. That "something" is most likely a piece of debris that got smashed into the ground electrode by the top of the piston.

Do you have a borescope? If so, try looking in the spark plug hole with it. I bet you'll find impact marks. Hopefully nothing serious! You may also find the piece of debris stuck in the top of the piston or the wall of the chamber.

 

The gap didn't close. The ceramic sleeve around the tip of the spark plug can just move up and down. Both pictures are of the same plug.

I don't have a boroscope, wish I did. But I just got my NGK plugs today and the factory gap is smaller than what I set on the Densos. We'll see how this works out tomorrow.

 

UPDATE: Problem is solved. Swapped in the NGK ILZKBR7B8DG plugs recommended for the JCW and my car runs like a dream. For future reference the Denso plugs I bought were SC20HR11s. They were even misfiring on the stock ECU map with the proper gapping. I'll have to look into the heat ranges of each to see if that was the problem.

 

Holy crap!!! OK, I misunderstood the pics. That's a very unhappy thing to have going on inside your engine, though. Glad you sorted it out; I'd be pretty upset about the plug failing like that.

 

I wish that I would have read this before ordering spark plugs today. Any chance they might work better in a n/a engine? If not...oh well, it's still not too late to return them and get some NGKs instead.

 

Glad this one worked out....

Only thing Denso Plugs are good for are is $$ for the mechanics who inevitably end up installing helicoils into your stripped out heads.....don't use them. They almost always loosen up and pop out due to improper density / composite of their plugs crush rings.

Use stock NGK for R56's.....

And buying plugs from Autozone for a MINI with all the different engines and year overlaps is about as smart as buying them on eBay, Neither source has proper charts to distinguish the correct application usually providing the wrong plug, for some that could mean punching holes in a few piston heads...

 

Again, I was just hoping to have a holdover until I got a set of proper NGKs come in. This wasn't going to be a long term fix. But I didn't think I'd have this many problems which is why I was concerned.

And no joke on Densos being expensive. They were basically double the price of NGKs.

 

MINI recommends 30k intervals for plugs on the JCW. With the tune you are basically a JCW so you are due for new plugs.